The invention relates to a multi-coordinate measuring machine with interferometric detection of the path of displacement in the respective measurement axes.
As a rule, such machines have three separate laser interferometers developed on the respective displacement-measurement axes X, Y and Z, each interferometer consisting of a laser, interferometer optics and photoelectric detectors for counting the lines or rings of the interference pattern. For example, a machine with such construction is described in published International Patent Application No. WO 81/02627. That machine has the disadvantage of relatively high cost, attributable to three separate laser generators which are incorporated into movable parts of the machine.
From West German C-2,109,954, it is already known to integrate the three axes of a processing machine into a single interferometric measuring system by sequentially performing each of the three displacement paths of measurement, one after another. The disadvantage of this solution is that to measure a given path of movement, the machine is limited to motion in only one axis at a time, while motion in the other two axes must remain stationary.
West German A1-3,201,007 describes an interferometric measuring machine in which measurement beams for the three displacement axes are produced, by beam splitting and reflection, from a single source of radiation. However, difficulties arise in correctly aligning the laser beam from a single source of radiation for supply to the interferometers of the individual measurement axes, since the interferometers are frequently at a great distance from each other, and vibrations, tilting of the movable machine parts, etc. interfere with transmission of the laser beam. To overcome these difficulties, the optical-mechanical design of the transmission channels is necessarily characterized by relatively great expense. Thus, a large number of carefully machined special prisms or mirrors is necessary for folding the beam, and it is also necessary to screen the transmission channel from dirt and outside light.